Formula One currently has only four manufacturers in 2015 season. This includes Mercedes, Ferrari, Renault and Honda. Currently it is only one team that is dominating the championship.
Other teams have clearly expressed their displeasure in this regard. With current F1 regulations in place, no teams are allowed to test or modify their vehicles during an ongoing season.
Now Honda made their re-entry into Formula One in 2015 season, however, they are struggling with pace, stability and many more issues. Other teams are also keen to enter the sport in the coming years.
Aston Martin is currently rumoured to provide engines to Red Bull Racing, who is currently using Renault engines. Their frustration with French manufacturer is evident and are not keen to continue with them.
Renault recently made it clear that they would focus their time in Formula E. They won the constructors championship of the inaugural season, which is a great achievement.
Mercedes currently own a minor stake in Aston Martin and if they join F1 will use Mercedes engine, which will be branded by Aston Martin. Difference will be that Aston Martin will take care of all technical advancements and development of this engine for Red Bull.